WASHINGTON — The bodies had not yet been fully recovered from the Amtrak derailment in Philadelphia before Capitol Hill erupted hours later into its usual partisan clash over how much money to spend on the long-struggling national rail service.

As investigators picked through the rubble on Wednesday morning, Democratic lawmakers in Washington angrily demanded an increase in Amtrak funding, calling Tuesday night’s accident a result of congressional failure to support the rail system. Republicans refused, defeating the request in a morning committee hearing and accusing Democrats of using a tragedy for political reasons.

“It was beneath you,” Representative Mike Simpson, Republican of Idaho, snapped at a Democratic colleague after the funding increase was defeated in a 30-to-21 vote.

The scene in the hearing room was a replay of the swirling politics that have threatened to consume Amtrak in the four decades since it was nationalized by the United States government. Like the rest of the country’s crumbling public infrastructure, its aging rail beds and decades-old trains are sagging under increased use, especially in the Northeast, where nearly three-quarters of all travel takes place on the trains, not on planes.

And the immediate political rancor foreshadowed another fight to come soon: whether Congress will delay a mandate to install equipment that would have automatically reduced the speed of Northeast Regional train No. 188. The deadline for installing the system, called positive train control, is the end of 2015, but Congress is considering extending the deadline to 2020 at the urging of freight and passenger rail systems that say the costs could rise to $10 billion.

Senator Richard Blumenthal, Democrat of Connecticut, said in a statement on Wednesday that delaying the technology “only leads to preventable and predictable tragedy.”

Investigators said they were examining the speed of the derailed Amtrak train, which they said was going 106 miles an hour on a stretch of track where the speed limit was half that. But they said no firm conclusion had been reached on what caused the derailment.

Edward G. Rendell, the Democratic former governor of Pennsylvania, lashed out at Republican lawmakers on Wednesday for refusing to increase Amtrak funding. He said the requested increase of $251 million over the Republican budget of $1.14 billion could significantly improve safety by upgrading tracks and installing positive train control systems in the busiest part of the system.

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The scene Wednesday at the accident site in Philadelphia. Some say better funding could have prevented the derailment.CreditNational Transportation Safety Board

“It is absolutely stunning to me,” Mr. Rendell said of the funding vote. “It shows that ideology trumps reality, and it shows that cowardice reigns in Washington. The callousness and disregard was shockingly contemporaneous.”

Representative Steve Israel, Democrat of New York, also criticized his Republican colleagues, saying they should have used the aftermath of the Amtrak accident “as an opportunity to do the right thing, instead of sticking to their ideology.”

The Northeast Corridor is the nation’s busiest rail corridor and accounts for more than a third of Amtrak’s ridership. It is also the most profitable part of its national network. But some bridges, like the Portal Bridge near New York, for instance, are more than a century old and in desperate need of replacement. Trains come to a crawl when they travel through Baltimore’s 100-year-old tunnel. Some parts of the tracks still have wooden ties.

Meanwhile, the Acela — Amtrak’s high-speed train that runs between Washington and Boston — can reach its top speed only in a handful of places. On a 30-mile stretch near Cranston, R.I., for example, the Acela speeds up to 150 m.p.h. About five minutes later, it needs to slow down.

“These trains have to be thought of as a national asset,” said Rosabeth Moss Kanter, a professor at the Harvard Business School. “Amtrak is a political whipping boy for Congress. But how much is it going to take to wake up Congress that this stuff has to be invested in? It is aging, it is not properly maintained.”

Amtrak has its passionate supporters, including Vice President Joseph R. Biden Jr., who often joins many lawmakers who race to Union Station for a quick trip home. But the rail system also has many detractors, who say its annual losses are a drain on the public treasury. Many argue that privatization of the rail lines would improve service, cut costs and create innovation that could rival the gleaming train systems in Japan, China and across Europe.

Representative John L. Mica, Republican of Florida, is pushing a plan to privatize the improvement of Amtrak’s system in the Northeast region. He said that the rail system needed money for improvements, but that lawmakers did not trust Amtrak to spend it well.

“What they own is poorly maintained and outdated infrastructure,” Mr. Mica said. But he added, “They don’t have the trust of Congress to get substantial money because they’ve not spent the money well that they’ve gotten.”

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The United States Naval Academy’s superintendent said Thursday that Justin Zemser, the midshipman who died in an Amtrak train derailment, was a talented and highly respected young man.CreditCreditU.S. Naval Academy, via Associated Press

“When you give them money, they squander it,” he said.

In the meantime, however, Amtrak’s funding is failing to catch up to its ridership, which peaked at 32 million last year, up nearly 50 percent since 2000. In 2014, its latest fiscal year, Amtrak lost $1 billion with revenue of $3.2 billion.

“Amtrak has really suffered from congressional schizophrenia over funding levels,” said Ray LaHood, the Republican former member of Congress who served as President Obama’s first secretary of transportation.

Mr. LaHood said much of the blame rested with lawmakers who came to Washington from states where Amtrak does not run. “They think Amtrak is just the easy place to cut,” he said, adding that he had little optimism that anything would change without pressure from voters during election time.

“All Americans should be concerned that there is no vision,” Mr. LaHood said. “There is no plan. There is no courage for taking up what needs to be done in terms of fully funding infrastructure. We are limping along.”

Since the passage of the Rail Passenger Service Act of 1970, the National Railroad Passenger Corporation, as Amtrak is officially called, is the only provider of national passenger rail service in the country.

Successive Amtrak chief executives — there have been six since 2002 — contend with a dual mandate: to provide a public service while also trying to make money, which has proved an impossible task, Ms. Kanter said. Her latest book, “Move: Putting America’s Infrastructure Back in the Lead,” addresses the importance of investing in transportation infrastructure.

“We have to do something big instead of just repairing. We need to repair, of course, but we have to reinvent, too, because the whole model is broken,” she said. “We don’t want to be stuck with the same crummy, shabby system after we fix Philadelphia. We have to do something more, and better.”

A version of this article appears in print on , Section A, Page 18 of the New York edition with the headline: One Day After Wreck, Increased Funding for Amtrak Fails in a House Panel . Order Reprints | Today’s Paper | Subscribe